1. Field of the Invention
The invention relates to an axial piston machine of the pivoting carriage type of construction, with an internal bearing-flushing system.
2. Discussion of the Prior Art
The starting point of the invention is an axial piston machine, such as is known, for example, from DE 42 15 869 C1. This published specification discloses an axial piston machine of the pivoting carriage type of construction. The known axial piston machine comprises a pivotable cylinder drum and a drive shaft mounted in a drive shaft bearing arrangement. The drive shaft is connected to a drive shaft flange in which pistons movable in cylinder bores in the cylinder drum are articulated and on which the cylinder drum is supported via a central journal. There is also provided, between the cylinder drum and a closing plate on the end face, a lens-shaped control mirror body which has control nodules for the cyclical connection of the cylinder bores to the working lines. A positioning arrangement, which is not represented in detail in DE 42 15 869 C1, is provided for tilting the cylinder drum, together with the control mirror body. In order to supply the drive shaft bearing arrangement with flushing agent, a flushing duct is provided in the central journal and in the drive shaft. The leakage oil draining out of the drive shaft bearing arrangement as a result of the flushing of the bearings is conveyed away in the direction of an opening in the housing by a vane wheel provided on the drive shaft flange.
From DE 36 38 890 C2, it is known practice to provide an axial piston machine of the oblique-axis type of construction having a constant, non-adjustable displacement volume, with a flushing agent duct which extends through the central journal and the drive shaft. The flushing agent is removed, by means of a valve needle which is displaceable in a pressure-dependent manner, from that control nodule of the control part which conducts low pressure.
However, this design solution cannot be used in axial piston machines of the pivoting carriage type of construction with a cylinder drum which is tiltable for the purpose of varying the displacement volume, without problems arising which cannot be overcome in practice. In particular, it has turned out that malfunctions of the valve needle occur if the control mirror body also impacts the stop means which determine the minimum and maximum displacement volumes in each case. The valve needle jams as a result of impact loads which arise in the process, and cracks can occur in the control mirror body In addition, the solution with an integrated valve needle which is known from DE 36 38 890 C2 has likewise proved unsuccessful because the bores and recesses necessary for receiving the flushing needle lead to a weakening of the control mirror body and the feeding pressure protection for the flushing agent is not constant because of the rotation and the pivoting movement of the cylinder drum and of the control mirror body. A further disadvantage is that the feeding pressure setting for the flushing agent cannot be set from outside, since the feeding pressure valve is not accessible from outside and the flushing valve integrated into the control mirror body depends upon the nominal size, since the distance between the control nodules is different for each nominal size of the axial piston machines. It has also turned out that the quantity of flushing agent introduced into the flushing duct by the flushing valve integrated into the control mirror body is inadequate for some applications.
For the reasons mentioned above, the solution known from DE 36 38 890 C2 for axial piston machines with a constant displacement volume has not proved successful in practice in the case of axial piston machines of the pivoting carriage type of construction with variable displacement volume.